Revert r340947 "[InstCombine] Expand the simplification of pow() into exp2()"

It broke the clang-cl self-host.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@340991 91177308-0d34-0410-b5e6-96231b3b80d8

Author: rnk

lib/Transforms/Utils/SimplifyLibCalls.cpp

@@ -13,7 +13,6 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/Utils/SimplifyLibCalls.h"
-#include "llvm/ADT/APSInt.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringMap.h"
 #include "llvm/ADT/Triple.h"
@@ -1184,13 +1183,12 @@ static Value *getPow(Value *InnerChain[33], unsigned Exp, IRBuilder<> &B) {
 }
 
 /// Use exp{,2}(x * y) for pow(exp{,2}(x), y);
-/// exp2(n * x) for pow(2.0 ** n, x); exp10(x) for pow(10.0, x).
+/// exp2(x) for pow(2.0, x); exp10(x) for pow(10.0, x).
 Value *LibCallSimplifier::replacePowWithExp(CallInst *Pow, IRBuilder<> &B) {
   Value *Base = Pow->getArgOperand(0), *Expo = Pow->getArgOperand(1);
   AttributeList Attrs = Pow->getCalledFunction()->getAttributes();
   Module *Mod = Pow->getModule();
   Type *Ty = Pow->getType();
-  bool Ignored;
 
   // Evaluate special cases related to a nested function as the base.
 
@@ -1251,28 +1249,10 @@ Value *LibCallSimplifier::replacePowWithExp(CallInst *Pow, IRBuilder<> &B) {
 
   // Evaluate special cases related to a constant base.
 
-  const APFloat *BaseF;
-  if (!match(Pow->getArgOperand(0), m_APFloat(BaseF)))
-    return nullptr;
-
-  // pow(2.0 ** n, x) -> exp2(n * x)
-  APFloat BaseR = APFloat(1.0);
-  BaseR.convert(BaseF->getSemantics(), APFloat::rmTowardZero, &Ignored);
-  BaseR = BaseR / *BaseF;
-  bool IsInteger    = BaseF->isInteger(),
-       IsReciprocal = BaseR.isInteger();
-  const APFloat *NF = IsReciprocal ? &BaseR : BaseF;
-  APSInt NI(64, false);
-  if ((IsInteger || IsReciprocal) &&
-      !NF->convertToInteger(NI, APFloat::rmTowardZero, &Ignored) &&
-      NI > 1 && NI.isPowerOf2()) {
-    double N = NI.logBase2() * (IsReciprocal ? -1.0 : 1.0);
-    Value *FMul = B.CreateFMul(Expo, ConstantFP::get(Ty, N), "mul");
-    if (Pow->doesNotAccessMemory())
-      return B.CreateCall(Intrinsic::getDeclaration(Mod, Intrinsic::exp2, Ty),
-                          FMul, "exp2");
-    else
-      return emitUnaryFloatFnCall(FMul, TLI->getName(LibFunc_exp2), B, Attrs);
+  // pow(2.0, x) -> exp2(x)
+  if (match(Base, m_SpecificFP(2.0))) {
+    Value *Exp2 = Intrinsic::getDeclaration(Mod, Intrinsic::exp2, Ty);
+    return B.CreateCall(Exp2, Expo, "exp2");
   }
 
   // pow(10.0, x) -> exp10(x)

test/Transforms/InstCombine/pow-1.ll

@@ -16,7 +16,6 @@
 
 declare float @powf(float, float) nounwind readonly
 declare double @pow(double, double) nounwind readonly
-declare double @llvm.pow.f64(double, double)
 declare <2 x float> @llvm.pow.v2f32(<2 x float>, <2 x float>) nounwind readonly
 declare <2 x double> @llvm.pow.v2f64(<2 x double>, <2 x double>) nounwind readonly
 
@@ -58,18 +57,18 @@ define <2 x double> @test_simplify2v(<2 x double> %x) {
 
 define float @test_simplify3(float %x) {
 ; ANY-LABEL: @test_simplify3(
-; ANY-NEXT:    [[EXP2F:%.*]] = call float @exp2f(float [[X:%.*]]) [[NUW_RO:#[0-9]+]]
-; ANY-NEXT:    ret float [[EXP2F]]
+; ANY-NEXT:    [[EXP2:%.*]] = call float @llvm.exp2.f32(float [[X:%.*]])
+; ANY-NEXT:    ret float [[EXP2]]
 ;
   %retval = call float @powf(float 2.0, float %x)
   ret float %retval
 }
 
+; TODO: Should result in exp2(-2.0 * x).
 define double @test_simplify3n(double %x) {
 ; ANY-LABEL: @test_simplify3n(
-; ANY-NEXT:    [[MUL:%.*]] = fmul double [[X:%.*]], -2.000000e+00
-; ANY-NEXT:    [[EXP2:%.*]] = call double @exp2(double [[MUL]]) [[NUW_RO]]
-; ANY-NEXT:    ret double [[EXP2]]
+; ANY-NEXT:    [[RETVAL:%.*]] = call double @pow(double 2.500000e-01, double [[X:%.*]])
+; ANY-NEXT:    ret double [[RETVAL]]
 ;
   %retval = call double @pow(double 0.25, double %x)
   ret double %retval
@@ -84,30 +83,30 @@ define <2 x float> @test_simplify3v(<2 x float> %x) {
   ret <2 x float> %retval
 }
 
+; TODO: Should result in exp2(2.0 * x).
 define <2 x double> @test_simplify3vn(<2 x double> %x) {
 ; ANY-LABEL: @test_simplify3vn(
-; ANY-NEXT:    [[MUL:%.*]] = fmul <2 x double> [[X:%.*]], <double 2.000000e+00, double 2.000000e+00>
-; ANY-NEXT:    [[EXP2:%.*]] = call <2 x double> @llvm.exp2.v2f64(<2 x double> [[MUL]])
-; ANY-NEXT:    ret <2 x double> [[EXP2]]
+; ANY-NEXT:    [[RETVAL:%.*]] = call <2 x double> @llvm.pow.v2f64(<2 x double> <double 4.000000e+00, double 4.000000e+00>, <2 x double> [[X:%.*]])
+; ANY-NEXT:    ret <2 x double> [[RETVAL]]
 ;
   %retval = call <2 x double> @llvm.pow.v2f64(<2 x double> <double 4.0, double 4.0>, <2 x double> %x)
   ret <2 x double> %retval
 }
 
 define double @test_simplify4(double %x) {
 ; ANY-LABEL: @test_simplify4(
-; ANY-NEXT:    [[EXP2:%.*]] = call double @exp2(double [[X:%.*]]) [[NUW_RO]]
+; ANY-NEXT:    [[EXP2:%.*]] = call double @llvm.exp2.f64(double [[X:%.*]])
 ; ANY-NEXT:    ret double [[EXP2]]
 ;
   %retval = call double @pow(double 2.0, double %x)
   ret double %retval
 }
 
+; TODO: Should result in exp2f(3.0 * x).
 define float @test_simplify4n(float %x) {
 ; ANY-LABEL: @test_simplify4n(
-; ANY-NEXT:    [[MUL:%.*]] = fmul float [[X:%.*]], 3.000000e+00
-; ANY-NEXT:    [[EXP2F:%.*]] = call float @exp2f(float [[MUL]]) [[NUW_RO]]
-; ANY-NEXT:    ret float [[EXP2F]]
+; ANY-NEXT:    [[RETVAL:%.*]] = call float @powf(float 8.000000e+00, float [[X:%.*]])
+; ANY-NEXT:    ret float [[RETVAL]]
 ;
   %retval = call float @powf(float 8.0, float %x)
   ret float %retval
@@ -122,11 +121,11 @@ define <2 x double> @test_simplify4v(<2 x double> %x) {
   ret <2 x double> %retval
 }
 
+; TODO: Should result in exp2f(-x).
 define <2 x float> @test_simplify4vn(<2 x float> %x) {
 ; ANY-LABEL: @test_simplify4vn(
-; ANY-NEXT:    [[MUL:%.*]] = fsub <2 x float> <float -0.000000e+00, float -0.000000e+00>, [[X:%.*]]
-; ANY-NEXT:    [[EXP2:%.*]] = call <2 x float> @llvm.exp2.v2f32(<2 x float> [[MUL]])
-; ANY-NEXT:    ret <2 x float> [[EXP2]]
+; ANY-NEXT:    [[RETVAL:%.*]] = call <2 x float> @llvm.pow.v2f32(<2 x float> <float 5.000000e-01, float 5.000000e-01>, <2 x float> [[X:%.*]])
+; ANY-NEXT:    ret <2 x float> [[RETVAL]]
 ;
   %retval = call <2 x float> @llvm.pow.v2f32(<2 x float> <float 0.5, float 0.5>, <2 x float> %x)
   ret <2 x float> %retval
@@ -170,7 +169,7 @@ define <2 x double> @test_simplify6v(<2 x double> %x) {
 
 define float @test_simplify7(float %x) {
 ; ANY-LABEL: @test_simplify7(
-; ANY-NEXT:    [[SQRTF:%.*]] = call float @sqrtf(float [[X:%.*]]) [[NUW_RO]]
+; ANY-NEXT:    [[SQRTF:%.*]] = call float @sqrtf(float [[X:%.*]]) [[NUW_RO:#[0-9]+]]
 ; ANY-NEXT:    [[ABS:%.*]] = call float @llvm.fabs.f32(float [[SQRTF]])
 ; ANY-NEXT:    [[ISINF:%.*]] = fcmp oeq float [[X]], 0xFFF0000000000000
 ; ANY-NEXT:    [[TMP1:%.*]] = select i1 [[ISINF]], float 0x7FF0000000000000, float [[ABS]]
@@ -331,6 +330,7 @@ define <2 x double> @pow_neg1_double_fastv(<2 x double> %x) {
   ret <2 x double> %r
 }
 
+declare double @llvm.pow.f64(double %Val, double %Power)
 define double @test_simplify17(double %x) {
 ; ANY-LABEL: @test_simplify17(
 ; ANY-NEXT:    [[SQRT:%.*]] = call double @llvm.sqrt.f64(double [[X:%.*]])